Guardrail systems are one example of traffic barriers placed along roadsides to screen errant vehicles from hazards behind the barrier. Guardrail systems are frequently constructed using steel W-beams mounted on wood or steel posts. Thrie beams may also be used as a guardrail system. Both W-beams and thrie beams function primarily in tension to redirect an impacting vehicle. Therefore, the ends of a typical guardrail system are securely anchored to allow the associated beams to develop desired tensile forces. In addition, since the ends of a guardrail system represent a discontinuity in the barrier, the end facing oncoming traffic is subject to being struck “head-on” by vehicles with small departure angles from an adjacent roadway. When struck in this manner, the end of the guardrail may spear the vehicle. One widely used, but now obsolete, end terminal design “buried” a W-beam at the end of the guardrail facing oncoming traffic to eliminate spearing.
Various types of highway safety devices are often disposed at the end of guardrail systems and other traffic barriers. Examples include guardrail end terminals, barrels filled with sand and crash cushions. Highway agencies have used crash cushions at high accident locations for a number of years. Crash cushions are generally provided to absorb the energy of head-on impacts with decelerations that are not life threatening for design conditions. Because the number of guardrail systems is quite large and impact probability is low for the end of most guardrail systems, many states often do not have sufficient resources to employ crash cushions at the end of all guardrail systems because of the associated expense.
Development of guardrail end terminals and crash cushion designs is complicated by the need to minimize resistance to small car impacts while still providing necessary energy absorbing capability for full-size car impacts. Such impacts may occur with the end or downstream from the end of a guardrail system or other traffic barrier. U.S. Pat. Nos. 4,655,434 and 5,957,435 to Maurice E. Bronstad, disclose guardrail end terminals having beams with spaced openings to absorb kinetic energy of an impacting vehicle.
The use of traffic barriers and particularly concrete barriers has become more common with respect to gore areas. The terms “gore” and “gore area” may be used to describe land where two roadways diverge or converge. A gore is typically bounded on two sides by the edges of the roadways which join at the point of divergence or convergence. Traffic flow is generally in the same direction on both sides of these roadways. The gore area generally includes shoulders or marked pavement, if any, between the roadways. Additionally, a gore area may extend sixty (60) meters (approximately two hundred (200) feet) from the point of divergence or convergence.